1. Field of the Invention
The present invention relates to a battery charger for an electric vehicle, and more particularly, to a forced discharge circuit of a battery charger for an electric vehicle, which is capable of forcibly discharging a high voltage in accordance with the electric safety code for electric vehicles when the function of the battery charger is stopped, a battery charger for an electric vehicle including the forced discharge circuit, and an electric vehicle having a function of the battery charger.
2. Description of the Related Art
Recently, as the problem of environmental pollution on the earth has become serious, the use of pollution-free energy has become more and more important. In particular, the problem of air pollution in big cities is becoming more serious, and exhaust gas of vehicles is one of main causes thereof.
In such a state, research has been actively conducted on so-called electric vehicles which use pollution-free energy, for example, electricity as power source. The electric vehicle receives electric energy from outside, charges the received electric energy in a battery, and then obtains mechanical energy through a motor coupled to wheels by using the voltage charged in the battery.
That is, since the electric vehicle drives the motor using the voltage charged in the battery, the electric vehicle uses a large-capacity rechargeable battery and includes a battery charger for charging the large-capacity rechargeable battery.
The battery charger may be divided into a quick battery charger and a slow battery charger, depending on a charging time. Furthermore, the battery charger may be divided into an onboard type battery charger and a mounting type battery charger, depending on whether the battery charger is built in a vehicle. The quick battery charger is installed in a place for quickly charging a battery during operation, such as a gas station, and the charging time thereof requires about 20 minutes. On the other hand, the slow battery charger is installed in a place, such as a parking lot or shopping mall, where the electric vehicle is expected to be parked for a long time, and the charging time thereof requires about five hours.
Recently, as the development and distribution of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) have been accelerated, the international standards (SAEJ 1772, IEC 61851-1 and the like) and the domestic standards (K 61851-1 and the like) related to a battery charger for EV/PHEV have been announced.
After input power is removed from a battery charger in operation, the internal voltage of an onboard battery charger (OBC) may be charged to a high voltage of, for example, DC 400V, which may cause electric shock.
In accordance with the electric safety code (UL 2202) for electric vehicles, a high voltage of a circuit within the OBC must be dropped to 60V or less within five seconds when the function of the OBC is stopped.
Therefore, there is a demand for a method that can forcibly drop a voltage within a predetermined time in accordance with the electric safety code for electric vehicles when the input power is removed from the OBC in operation.